AB0099 KNEE SYNOVIAL FLUID AND SERUM TNF-α IN RHEUMATOID ARTHRITIS: CORRELATION WITH SONOGRAPHIC PARAMETERS
Authors: A. H. El Hassaany, S. Tharwat, M. Mansour, A. F. Enein
Journal: Annals of the Rheumatic Diseases (2022)

Background Rheumatoid arthritis (RA) is a chronic, inflammatory joint condition that affects about 5 out of 1000 persons of the general population [1]. Environment, genetics, and autoimmunity may all have a role in the pathogenesis of the disease [2]. Overproduction of pro-inflammatory cytokines like tumor necrosis factor-α (TNF-α) is the end result of these mechanisms [3].However, little is known about its soluble concentrations in synovial fluid and serum and its association with clinical and ultrasonographic joint parameters. Objectives The aim of this study was to assess the presence of TNF-α in serum and synovial fluid of the knee in RA patients with knee effusion and to evaluate its correlation with musculoskeletal ultrasound (MSUS) parameters of the affected knee joint. Methods This study included 40 patients (20 RA,10 systemic lupus erythematosus (SLE) and 10 osteoarthritis (OA)) who had knee effusion (unilateral or bilateral) upon clinical examination. The sample size was selected as convenient sample; all patients who fulfilled the inclusion criteria were offered to participate in the study, unless they qualify for any of the exclusion criteria or refuse to participate. The inclusion criteria included the following: a) age ≥ 18 years old, b) patients with knee effusion detected by clinical examination and confirmed by MSUS, c) patients with RA diagnosed according to 2010 ACR /EULAR classification criteria [4],SLE according to SLICC criteria [5] or knee OA diagnosed according to EULAR criteria [6]. Demographic, clinical, and therapeutic data were recruited from all participants. Visual analogue scale (VAS) was used to determine the pain intensity in the affected knee. MSUS examination of the affected knee was performed, and a sample of synovial fluid was aspirated. TNF-α was measured in the aspirated synovial fluid and serum of each patient. Results There was a total of 40 patients (20 RA, and 20 age and sex matched non_RA (10 SLE, and 10 OA)). The mean age of RA patients was 48.4 years, most of them were females (80%) with median duration of knee pain of 2 months. Serum TNF-α was barely significantly higher in RA vs. non-RA cases (3.66 ± 0.76 vs 3.24 ± 0.58 U/ml, p= 0.052), while in synovial fluid, difference was not statistically significant (3.73 ± 0.72 vs 3.48 ± 0.58 U/ml, p= 0.252). Also, there was a statistically significantly higher serum TNF-α in RA vs. OA (3.66 ± 0.76 vs 3.06 ± 0.32, p= 0.022). Figure 1 shows that serum TNF-α at cut point of &gt;3.24 U/ml can significantly discriminate RA from OA with 65% sensitivity, and 90% specificity (AUC = 0.725, P = 0.018). There was no statistically significant correlation between synovial TNF-α and MSUS parameters of thee knee either in RA or non_RA patients. Figure 1. ROC curve for serum TNF as a discriminator of RA from non-RA Conclusion Serum TNF-α is higher in RA than non_RA patients. However, synovial fluid TNF-α level do not differ in RA from non_RA patients. No role of synovial TNF-α in knee pathologies in RA patients. References [1]Aletaha, D. and J.S.J.J. Smolen, Diagnosis and management of rheumatoid arthritis: a review. 2018. 320 (13): p. 1360-1372. [2]McInnes, I.B. and G.J.N.E.J.o.M. Schett, The pathogenesis of rheumatoid arthritis. 2011. 365 (23): p. 2205-2219. [3]Smolen, J.S., D. Aletaha, and I.B. McInnes, Rheumatoid arthritis. Lancet, 2016. 388 (10055): p. 2023-2038. [4]Kay, J. and K.S.J.R. Upchurch, ACR/EULAR 2010 rheumatoid arthritis classification criteria. 2012. 51 (suppl_6): p. vi5-vi9. [5]Petri, M., et al., Derivation and validation of the Systemic Lupus International Collaborating Clinics classification criteria for systemic lupus erythematosus. 2012. 64 (8): p. 2677-2686. [6]Zhang, W., et al., EULAR evidence-based recommendations for the diagnosis of knee osteoarthritis. 2010. 69 (3): p. 483-489. Disclosure of Interests None declared